Tractors used for pulling semi-trailers are commonly equipped with two external rear view mirrors, these mirrors generally being rectangular and mounted on brackets extending laterally from opposite sides of the tractor cab with provision for at least direct manual adjustability about the vertical axes of the mirrors to provide the driver with views rearwardly along the sides of the trailer. When a tractor trailer turns, the tractor rotates relative to the trailer about the fifth wheel and, with the conventional fixed position rear view mirror installations, the lines of sight of the mirrors likewise rotate relative to the trailer so that the mirror on the side of the turn is aimed toward the side of the trailer, preventing the driver from viewing completely the area to that side of the trailer. Due to the greater distance between the driver and the right or off side mirror than that to the left mirror, the field of view provided by the right mirror is quite narrow, about 2.degree., and, consequently, the problem of obstructed rear vision on this side during turning maneuvers is of particular concern.
In order to overcome this problem, a number of mirror positioning systems have been devised. Among these are driver actuated remote positioning systems such as those shown in U.S. Pat. Nos. 4,792,220, Janowicz and 4,798,967, Yamana et al. A disadvantage of such systems, however, is that their operation requires the driver to divert attention from steering and watching conditions forward and lateral of the vehicle. Positioning systems for automatically rotating the mirror in response to changes in the angular relation of the trailer to the tractor eliminate the requirement of driver intervention. These systems include ones employing mechanical linkages, for example, the systems disclosed in U.S. Pat. Nos. 2,988,957, Kotora, Jr.; 3,166,630, Esslinger; 3,208,343, Prochnow; 3,527,528, McKee et al.; 3,536,382, McKee et al.; 3,640,608, McKee et al.; 3,761,164, McKee et al. and 3,950,080, McKee et al., and ones having rotation sensors and electrical controls for mirror rotation, examples of which are shown in U.S. Pat. Nos. 3,469,901, Cook et al.; 3,749,480, De Witt et al. and 4,609,265, McKee et al. The relative complexity of these latter systems, the requirement of modification of either or both the tractor and the trailer and the loss of flexibility in the use of a given tractor with many trailers have limited the adaption of such systems.
When a tractor trailer is turning, the trailer does not directly follow the path the tractor. Rather, the rear wheels of the trailer follow a path offset in the direction of the turn so that there is lateral movement of the trailer in this direction and this effect is more pronounced with longer trailers. This trailer lateral movement poses a serious risk of accident resulting from collision of the side of the trailer with an individual or object in the area in close proximity to the turning side of the tractor trailer. Rear view mirror systems which automatically rotate the mirrors to maintain vision along the side of the trailer during turning are of some value in preventing such accidents. However, during a turning maneuver the truck driver's attention is normally directed primarily to conditions forward and to the opposite side from the turn of the vehicle and serious accidents have occurred when, for example, another motorist or a bicyclist has attempted to overtake the tractor trailer on the turning side or a pedestrian has stepped in to the path of travel of the turning trailer. Among the precautions now taken against such accidents is the use of a placard displayed on the rear of the trailer bearing a legend such as "CAUTION! THIS VEHICLE MAKES WIDE TURNS!" Such a warning is of only limited value. Auxiliary convex mirrors are also used to provide increased rearward vision but such a mirror severely distorts the perspective of the image, limiting its effectiveness.
It is the primary object of the present invention to provide a positioning system for a rear view mirror of a tractor which automatically rotates the mirror to provide clear vision along the side of an attached trailer at all times.
It is also an object of the present invention to provide such a mirror positioning system which is self-contained in that the system does not require either mechanical linkage or electrical signal connections between the tractor and the trailer or with the steering mechanism of the tractor.
A further object of the invention is the provision, in conjunction with a rear view mirror of a tractor-trailer, of means for alerting the driver of any intrusion into the zones to the sides of the trailer.